Ingot mold and method of making same



QFFICE.

Gr. COATLES, 03E PASADEIHL OALEYEGRNIA, ASSIGNUR TO VALLEY MOULD AND IRON CORPOIRATIQN, Q1? YORK INGOT No Drawing.

To all 1.071 cm 2'75 may conccm Be it known that I, RAY G. Collins, a citizen of the United States, residing at Pasadena, in the county of lies Angeles, State of California, have invented certain new and useful llmprovements in ingot Molds ant lllethods ot hflahing Same, of whichthe following is a specification.

This invention relates broadly to metal.- lurgry and more specially to ingot molds used for casting steel ingots.

The principal object of my invention is to increase the number of heats an ingot mold will stand before it becomes unlit for service.

Another object is to provide an ingot mold having the mold wall portion adjacent the matrixof the mold under tension at nornial ten'iperatul'es.

A further object of the present invention is an ingot mold wherein the normal conditions of stress in mold alls is reversed when the mold is filled with molten metal.

A still further object of the present invention is to provide an ingot mold wherein the outer portion of the mold walls is chilled metal and the inner portion of the mold walls is non-chilled metal.

Other and further objects of the present invention will in part be obvious and will in part be pointed out hereinafter in the specification following.

Realizing that the present invention may he carried in constructions other than those herein specifically described it is desired that the disclosure shall be understood as illustrative and not in the limiting sense.

Vvhen a common annealed ordinary mold, at normal temperature, is filled with fluid seel the inner surfaces of the mold become rapidly heated from the intense heat of the hot metal. This heat is conducted through the mold walls to the outer surfaces and from these surfaces is dissipated by convection and radiation, Since the inner surfaces are more quickly heated by the fluid steel than a parallel Zone in the mold walls, these inner portions of the mold walls tend to ca;- pand. and since any expansion is resisted by the still cool outer portion of the walls, a heavy stress of compression results on this part first heated. The effort to expand puts a strong tensile stress on the outer portion of-the walls which resist this expansion so Application filed August 17, 1922.

.EVKHLE, PENNSYLVANI A CORPORATION OF MOLD AND METHOD OF MAKING SAME.

Serial No. 532,545.

that a condition of considerable stress between the inner and outer parts of the walls results. The expansion of the inner portion of the walls is restrained by a tensile stress on the outer portion of the walls and there fore a high compressional stress exists all over the inner portion of the walls. Thus a very heavy tensile stress occurs in the outer portion of the walls at the time the heat reaches the outer surface of the mold. Durmg" this time the inner zone of the mold walls has passed from a condition of no stress to one of high compression. These stresses continue to grow until the heat reaches the outer walls and the heat gradient becomes more or less stable. From this time both walls rise in temperature, although not necessarily at parallel rates, until the highest points reached by the inner walls is attained. At normal temperature the walls of the ordinary mold are as nearly neutral as to all internal stresses as ordinary annealing in the sand will accomplish. When the ordinary mold is filled the stresses in the walls are all in one direction from the neutral condition, a compressional stress on the inner walls and tensile stress on the outer walls.

My improved mold is so cast that when the improved mold is at normal temperature the inner zone of the mold walls is in a state of tension instead of one of neutrality as in the common mold, which tension is resisted by a compressional stress on the outer Zone of the mold walls. This condition of stress may be produced by any of the usual controllable methods now practiced in the foundry which results in strained castings. In casting my improved mold the cooling of the outer walls is to be accelerated as regards that of the inner walls. It is most readily effected by casting the inner surface of the mold against a surface of small heat absorbing capacity and the outer walls against one whose heat absorbing capacity is relatively larger. This more rapid cooling of the outer walls is not carried to the extent of a quick chilling of the outer surface of the mold so as to harden it in the commonly accepted sense of chilled metal. although this n'ieta-l may be considered having been chilled in the sense that the heat has been rapidly ab sorbed.

The flask part of theinold in which the ingot mold itself is cast should have a heat absorbing capacity such that the outer wall of the mold will set promptly while the inner *all is to be kept hotter by being cast over a dried core, of such construction as to have a small heat absorbing capacity, as to not set the inner wall of the mold so promptly as the outer wall. The di'll'erence in setting and cooling rates causes the outer walls to build up somewhat more rapidly than the inner walls, which latter are therefore at a higher temperature so that as the mold cools down a heat gradient runs from the inner surface towzurds the outer surface of the mold walls. it the final end of cooling the inner portion of the walls having cooled later than tle outer portion of the walls from the temperature oi lluidity and setting, these inner portions arrive at normal temperature in a state of tension tor the reason that the outer portion of the i lls had practically ceased to contract while the inner portions of he walls ltept on contracting until it reached norn'ial temperature. This differential ellect is rendered possible by the great thicki ess of the rails of ingo molds. These final strains are not to be removed by annealing. W hen the metal has solidified so that there is no danger of bleeding the cooling of the outer portion of the *alls may be accelerated by removing the flash from the casting and letting the air carry oil the heat at a more rapid rate, with the secondary ad 'antagre oi. releasing the equipment for other work. The inner portion of the wall, however, is to be pro tected from cooling etle-cts by being kept in contact with the core sand until the mold cool.

The improved cool mold is thus in a dition o't tension tl'iroughout the inn-er portion oi its walls, which tension is resisted h a compressiona1 strain on the outer res n'zaining thickness ot the walls.

hen l'luid steel is poured into such a nold the heat tr: vels hy conduction through the meld walls towards their outer surtace and simultaneously wi" this conduction the inner walls tend to begin to expand. wince these inner walls ire initially under tension this tende cy has the effect of reducing the tension. it reduction of tension on the inner walls simultaneously reduces the coinpressional stress on the outer walls. The continued conduction of heat from the inner towards the outer walls, with its accompanyii expansion, finally brings the heat to the outer sur' acc.

in this course ot cvents at some point in the rise temperature oi the inner walls a point is reached where the expansion the walls neutralizes the initial tension :1 corresponding loss of the compr strain on the outer wall esults. state the mold is about in the condition of a. common annealed mold as it stant s at normal tei'nperature readly tor a neatf a very important ditl'ercnce, however, tor the common in id is without rains whcn cold, while my improved mold witnou; strains when already well heated tow: the maximum temperature it will a this condition of neutrality is, ot' course. of brief duration tor the tempo ature o the walls keeps rising and the inner rzlls develop a compressional stress became o their continued expansion. Fiin'mltaneous y be- ?ause ot this rising; onipressional stress on the inner walls, the out r walls develop tensile stresses, and both oi these sti crease until the heat gradient lron' ner to the outer walls has become est after which the temperatures continue to rise in both walls, although necessari v at parallel rates, with a stress condition more or less unvarying.

The condition 01'. the inner Va 'esses 1 the in .1 1 t iisiuu nut llic

mold hay changed from 2 tensi: cross to a condition of neutrality and then to a condit The lluid on oi compression stress. 1 ellecl' ange from the neutral condition heinn each way, tensile and con'ipressional. that the maximum stresses each aich the inner walls immediately compressive stress from the be j the heat so that the 1 1m strain point reached represent-i a de- 1 .re i Join the neutral poinl much greati than in the case oil my improved mold. inns in my mold the inne and outer wall; experience both tensile and compre. -:sirc stresses. in the old mold the inner walls 1. ctnnpressional stresses while the ouic na ls receive only ensile stresses from the h gjnnnin ot a heat.

it is custo nary to dry i molds and to u'cs used in tomary in casting my improved mold th; dried core built up on a pla core bar may be used. last flask tilled with sand. a i Slllllilbl, thickness and inter closely approximating the mold may he used and the i may be coated with slin'rv. wash, or brush coat I i i that will act as a non-ironed Any mechanical means oi aonlrinr :1 e O fltt't of the coatin is mid a chillin r action ot th surface it the mold bei ably faster on the outer portion of the walls than along the core. The flask may be made in several places, if necessary, in order to release the casting or to facilitate making of the flask, or to arrange special pockets for lug molds or staples to be applied in a completed form to the flask. When such a flask is used it will be well heated after casting and may then be cooled down to a reasonable temperature in water and still have enough heat left in it to quickly dry any coating that may be applied to its interior. Thus when the cycle of operations has been started no other heat than that furnished fromthe operations of casting will be necessary in order to dry any coating applied to the flask.

l do not confine myself to a metal flask as above described. Any means known to the founders art which will effect the differential rates of cooling as herein set forth I contemplate using.

The effect of heat due to the continued use of the mold may gradually eliminate the strains arranged for in the casting operation. In this case a part of the useful life of the mold will have already passed before the above mentioned condition is reached and the mold will then be in the condition, as to internal strains, of a common mold at the beginning of its period of service.

My invention applies to the common form of ingot mold for casting vertical steel ingots but may be applied to other forms of molds when these latter are so shaped that the strains arranged for the inner parts of the walls may be properly resisted by the outer parts.

Having thus described my invention, what l claim is:

1. A. cast metallic ingot mold having the inner portion of its walls in a state of tension in all directions in planes parallel with the surface of the matrix of said mold when said mold is at normal temperature.

2. A cast metallic ingot mold whose inner walls are so stressed in tension at normal temperature that the stresses are removed by the introduction of hot metal into said mold.

An ingot mold whose inner walls are so stressed at normal temperature that said strains are removed and then built as stresses of the opposite character by the introduction of hot metal into said mold.

t. An article of manufacture comprising a cast metallic ingot mold wherein the con ditions of stress in the metal. of the walls of the mold adjacent the inner and outer surfaces thereof is reversed when the mold is filled with molten metal.

An article of manufacture comprising a metallic ingot mold having zones of metal under tension adjacent the inner portion of the wall when the mold is at normal temperature.

6. An article of manufacture comprising a cast metallic ingot mold having the metal under compression adjacent the outer portion of the wall when the mold is at normal temperature.

7. An article of manufacture comprising a metalic ingot mold having the outer por tion of the mold wall chilled and the inner portion of the mold walls non-chilled.

8. An article of manufacture comprising an unannealed metallic ingot mold wherein the tensile and compressive strains existing in the metallic walls of themold adjacent the inner and outer surfaces thereof are re versed when the mold is filled with molten metal.

9. The method of casting an ingot mold which comprises providing a core of small. heat absorbing capacity, surrounding said core with a metallic flask of relatively high heat absorbing capacity, filling the space be tween said core and said flask with molten metal and permitting it to cool to normal temperature therebetween.

10. The method of casting an ingot mold which comprises providing a core of small heat absorbing capacity, surrounding said core with a flask of relatively high heat absci-bingcapacity, filling the space between said core and said flask with molten metal and retaining said flask and said core in position until said mold is substantially cooled to norniial temperature.

11. The method of casting an ingot mold which comprises providing a sand core of small heat absorbing capacity, surrounding said core with a metallic flask of relatively high heat absorbing capacity, filling the space therebetween with molten metal, retaining said core in position until said mold is cooled and removing said flaskwhen said mold is partially cooled to accelerate the cooling of the outer walls thereof.

12. The method of casting an ingot mold which comprises providing a sand core of small heat absorbing capacity, surrounding said core with a suitable flask, filling the space therebetween with molten metal and accelerating the cooling of the outer walls of the mold by removing the flask whereby the outer wall of the mold is cooled more rapidly than the inner wall thereof and the inner walls are set with tensile stresses at normal temperatures.

13. The method of casting an ingot mold which comprises freezing and cooling the inner walls of the mold at a slow rate and at the same time freezing and cooling the outer walls at a rapid rate, whereby the inner walls of the mold are set with tensile stresses at normal temperatures which decrease in value when the temperature of the mold is increased.

RAY G. GOATES. 

